The present invention generally relates to data acquisition system and more particularly to a data acquisition system which receives analog input information, converts the analog input information to multiple-bit digital data, and provides the digital data in a bit parallel format for storage in memory and subsequent processing by a digital control unit.
There are many systems which digitally process data which was originally acquired in analog form. One such system is a control system commonly referred to as a facility management system.
Facility management systems are generally used to control the internal environment and provide security and fire alarm monitoring of, for example, an office building or plant facility. Internal room temperature, humidity, air flow, lighting, security, and fire alarm are among some of the conditions controlled and/or monitored by such systems. These systems provide this kind of control largely in response to analog information obtained from remote sensors which are connected by multiple wires back to the control systems. Such multiple wires are necessary to both convey the information relative to the condition sensed back to the control system and to enable the control system to provide power to those remote sensors which require external power. Because many different types of conditions are controlled by such systems, many different types of remote sensors may be utilized in such systems.
Since many different types of remote sensors may be required in a particular control system configuration, the analog information provided by the remote sensors can be represented by many different types of analog parameters. For example, a temperature sensor may provide an indication of the temperature sensed in the form of a resistance parameter. Other remote sensors may provide a voltage magnitude indicating the conditions sensed, and still other remote sensors may provide a current magnitude indicative of the condition sensed. In each such case, the information provided by the remote sensor is in analog form.
The control portion of facility management systems usually includes a plurality of input channels for receiving the analog information from the remote sensors. In order to read the analog information from the remote sensors, an improved control system disclosed in U.S. patent application Ser. No. 07/387,019 filed July 28, 1989 in the names of Gregory A. Pascucci and John Pierson, entitled Universal Analog Input, includes an interface which adapts each input channel for reading any type of analog information which may be conveyed to it by a remote sensor. The interface there disclosed converts the type of analog information provided by a remote sensor to the type of analog information which is readable by the input channels of the system. In addition, the interface is selectively operable for converting any one of the different types of analog information to a given type of analog information readable by the system inputs.
Facility management systems, of the type to which the present invention is directed, include a digital control unit or module which digitally processes data received from the remote sensors. As a part of this process, it is necessary for the digital control module to convert the analog information read at the system inputs to digital data to enable the digital processing of such data. Because facility management systems provide control of voltages and currents of relatively high magnitude at points in close proximity to the digital control module, the digital control module is thus located in an area of relatively high electrical noise. In addition, some of the devices controlled by such systems may be electrical motors or the like which can themselves generate electrical noise on the conductors which provide control of such devices.
Since the digital control modules process digital data having voltage magnitudes of comparatively low levels, it is necessary to assure that the digital data being processed is not subject to electrical noise interference. While shielding of the digital control module provides some degree isolation of the digital signals being processed from electrical noise, shielding alone is not sufficient to assure reliable digital processing of digital data within such systems.
It is therefore a general object of the present invention to provide a new and improved data acquisition system which receives analog input information and converts the analog information to digital data which is immune to electrical noise.
It is a further object of the present invention to provide a data acquisition system for receiving analog information which converts the analog input information to multiple-bit digital data and provides the digital data in a bit-parallel format for storage in memory and subsequent use by a digital control module.
It is a further object of the present invention to provide a data acquisition system which includes a plurality of inputs for receiving analog information, and which converts the analog information received at each such input to parallel bits of data for subsequent use by a digital control module wherein the parallel bits of data are immune from electrical noise.
It is a still further object of the present invention to provide a control system of the type which responds to analog input information received from a plurality of remote sensors and of the type which includes a digital control module for digitally processing the information received from the remote sensors, the control system including a data acquisition system for acquiring the remote sensor analog input information and converting the analog input information to parallel multiple-bit digital data for use by the digital control module, wherein the parallel multiple-bit digital data is immune from electrical noise.
It is a still further object of the present invention to provide such a data acquisition system which generates internal data transfer enable clock and control signals which are also immune from electrical noise to assure reliable provision of the digital data for use by the digital control module.